This invention relates to the field of tape storage cartridges which include a rotatably mounted reel on which is wound a tape media. In particular, the invention relates to a tape storage cartridge having a reel on which the tape media is protected from physical damage.
Tape media, such a magnetic tape, is a common medium for the storage of data to be utilized by a computer. Magnetic tape has found widespread use as a data storage medium because it provides a relatively inexpensive solution for storing large amounts of data. There are, however, some problems with the methods previously used to store magnetic tape that can cause damage to the magnetic tape media. This damage results in errors when reading or recording data on the magnetic tape.
Magnetic tape is stored on cartridges of which there are a variety of different types and sizes. One reason for the variety of cartridge types is the variety of different tape drives in which the cartridges are used. Tape cartridges are comprised essentially of a cartridge shell which houses a rotatably mounted reel. Magnetic tape is wound around the hub of the reel. Reel flanges are used to contain the magnetic tape as the magnetic tape is wound on the hub. A fully loaded tape cartridge has magnetic tape wound around the hub such that the multiple layers of tape form a stack of magnetic tape extending out to near the end of the reel flanges.
The tape cartridge is inserted into a tape drive mechanism which automatically threads the magnetic tape from the tape cartridge through the tape guide mechanism of the tape drive assembly. The tape is then available to the tape drive mechanism for the reading and writing of data.
Data is recorded on magnetic tape in a specific format. The ability of a tape drive mechanism to read data from a piece of magnetic tape is contingent upon the data existing on the tape at positions according to the specific recording format. If a read head is aligned with a segment of magnetic tape in order to read a certain data track but instead a different data track is adjacent the read head, errors in reading the data occur.
One way to ensure that the magnetic tape medium is properly aligned with the read/write heads of the tape drive-mechanism is to use the edge of the magnetic tape medium as a reference position. If, for example, a tape cartridge is loaded with xc2xdxe2x80x3 magnetic tape, a tape edge guide mechanism in the tape drive is used whereby one edge of the magnetic tape is kept flush against the tape edge guide. If the width of the tape is constant, xc2xdxe2x80x3 in this example, then each track on the magnetic tape is in a known location, according to the recording format of the tape, relative to the read and write heads of the tape drive.
If the edge of a segment of magnetic tape is not straight, the tape edge guide mechanism is not able to properly align the magnetic tape. This can occur when the magnetic tape has been somehow damaged causing a crease, wrinkle, or other deformity, in the edge of the tape. When the damaged portion of the magnetic tape moves along the tape guide, the position of the magnetic tape with respect to the read and write heads is incorrect and, to some extent, unknown. Errors can then result when reading data from the tape. Typical tape drive devices include a control unit programmed in such a way, through error correction routines, to detect when errors of this type occur. However, even if the error is detectable, there may be no way to read certain data from a damaged tape. These errors are sometimes called permanent errors and can be critical depending on the extent and type of data that is lost.
It is therefore important that tape loaded in a tape cartridge remain undamaged. Tape cartridges are subject to various forms of physical stress and shock. Magnetic tape is often used for long term storage of data for periods of many years therefore the cartridge must protect the tape not just when the cartridge is new but also after many years of physical handling.
Magnetic tape stored in prior art tape cartridges is susceptible to damage when the tape cartridge suffers a physical shock, such as when it is dropped. As described above, magnetic tape is wound on the hub of a reel. The reels have flanges extending from the hub which are flared slightly so that the distance between the flanges is greater at the outer edge of the flanges than the distance between the flanges immediately adjacent the hub. This is because allowance must be made for air to escape from between the layers of tape as the tape is wound on the hub.
It is also necessary to provide an amount of clearance between the reel and the cartridge shell so that the reel can move, to a limited extent, independent of the position of the shell. This clearance is required to allow the reel to be engaged by the motor drive of the tape drive mechanism when the cartridge is inserted into the tape drive mechanism.
Sometimes when the tape is winding on the hub, a layer of tape is wound offset from the rest of the stack of tape wound on the hub. This results in what is termed a xe2x80x9cpop strandxe2x80x9d or xe2x80x9cstagger wrap finxe2x80x9d which is a single layer, or a grouping of layers, which are not edge for edge aligned with the remainder of the tape wound on the hub. The stagger wrap fin extends into the space between the edge of the stack of tape and the adjacent flange. If the cartridge is dropped on the floor and lands on a corner of the cartridge, the shock of the impact can force the outer edge of the reel flange to contact the cartridge shell. This causes the outer edge,of the reel flange to flex inwardly in the direction of the other reel flange, thereby reducing the distance between those reel flanges. In this event, a stagger wrap fin can be pinched between the reel flange and the stack of tape. When a stagger wrap fin gets pinched between the reel flange and the stack of tape, a crease is formed in the tape comprising the stagger wrap fin. Creases in the tape edges destroy the straight, consistent tape edge necessary for error-free operation of the tape drive mechanism.
If the edge of the tape is damaged, then the tape does not thread properly in the tape drive mechanism. When the damaged tape edge passes along the tape edge guide mechanism, the tape is improperly aligned relative to the read and write heads of the tape drive device. This results in errors when reading data from the tape or writing data to the tape. These errors may be, as described above, permanent errors which cannot be corrected through error correction codes. Permanent errors can be catastrophic depending on the criticality of the data that is lost.
Tape cartridges containing, for example, magnetic tape, are often used in automated data storage libraries. Such automated media storage libraries are known for providing cost effective access to large quantities of stored media. One (or more) accessor typically accesses the tape cartridges from a plurality of storage slots and delivers the accessed tape cartridge to a data storage drive for reading and/or writing data on the accessed tape cartridge. Suitable electronics both operate the accessor and operate the data storage drives to transmit and/or receive data from an attached on-line host computer system.
In a conventional automated media storage library, the storage slots are arranged in a planar orthogonal arrangement forming a xe2x80x9cwallxe2x80x9d of storage slots for holding data storage media. The plane may be a flat plane, or may be a cylindrical plane. To double the storage capacity, two xe2x80x9cwallsxe2x80x9d of storage slots may be provided on either side of the accessor.
There exists a need for tape a cartridge that better protects the magnetic tape wound on the cartridge. In particular, there exists a need for a tape cartridge that is less susceptible to damaging the edge of a magnetic tape wound on the cartridge. Such an improved tape cartridge comprises a useful improvement to an automated data storage system.
Applicants"" invention includes a tape cartridge having a shell formed from a top side and a bottom side. This shell comprises a top surface and an inner surface. Applicants"" apparatus further includes a reel rotatably disposed within said shell. This reel includes a hub having a first side and an opposing second side. The reel is rotatable disposed with the shell such that its first side is disposed adjacent the inner surface of the top side of the shell.
The hub portion of Applicants"" apparatus includes an aperture internally disposed therein and extending through the first side of the hub. In one embodiment, this aperture is circular is shape and the walls of the aperture comprise a cylindrical surface.
An annular ring having a first side, an opposing second side, a first surface and an opposing second surface, is disposed on the aperture""s cylindrical surface such that the second side extends inwardly from the cylindrical surface toward the center of the aperture. The first surface of the annular ring has a facing relationship with the inner surface of the top side of the shell.
Applicants"" apparatus further includes a first piloting member having a proximal end and a distal end. The proximal end of this first piloting member is disposed on the inner surface of the top side of the shell, and the distal end of this first piloting member extends outwardly from the inner surface such that this distal end of said first member is positioned adjacent the first surface of the annular ring. Applicants"" invention includes a second piloting member having a proximal end and a distal end. The proximal end of this second piloting member is disposed on the inner surface of the top side of the shell, and the distal end of this second piloting member extends outwardly from the inner surface such that this distal end of the second piloting member is positioned adjacent the first surface of the annular ring. In other embodiments, three or more piloting members are disposed on the inner surface of the top side of the shell such that their corresponding distal ends are positioned adjacent the top surface of the annular ring disposed in the aperture.
The gaps between the two, three, or more, piloting members and the top surface of the annular ring are adjusted in order to limit the rotation of the reel within the shell. In addition, the gaps between the two, three, or more, piloting members and the cylindrical wall of the aperture are adjusted to limit the lateral movement of the reel within the shell.
In other embodiments, Applicants"" apparatus includes an annular member disposed on the inner surface of the bottom side of the shell. This annular member extends into an annular groove disposed on the bottom side of the reel. The gap between the top of the annular member and the floor of the annular groove is adjusted to limit the rotation and lateral movement of the reel within the shell.